Abstract
LONDON. Royal Society, June 19.—Sir Archibald Geikie, K.C.B., president, in the chair.—Sir James Dewar: Atomic specific heats between boiling points of liquid nitrogen and hydrogen.—I. The mean atomic specific heats at 50° absolute of the elements a periodic function of the atomic weights.—Hon. R. J. Strutt: An active modification of nitrogen produced by the electric discharge. V. (1) An improved practical method of preparing and storing nitrogen for the experiments is described. (2) It is shown, notwithstanding criticisms of certain other experimenters, that the presence of traces of oxygen in the nitrogen used is not essential, or even favourable, to the phenomena. The nitrogen used, purified by cold phosphorus, does not contain oxygen to the extent of one part in 100,000. Passing it over red-hot copper in addition makes no difference. The intentional addition of oxygen does harm; 2 per cent, obliterates the effects altogether. Hydrogen and carbon dioxide as impurities are much less harmful, but traces even of water vapour have a very bad effect. (3) Nitrides are formed by the admixture of active nitrogen with vapour of mercury, cadmium, zinc, arsenic, sodium, and sulphur. These are decomposable by water or potash solution, yielding ammonia. (4) Carbon disulphide yields a blue polymeric nitrogen sulphide, and polymeric carbon monosulphide. Chloride of sulphur gives ordinary yellow nitrogen sulphide. Stannic chloride and titanium tetrachloride also yield solid products. In the latter case nitrogen was proved to be present. (5) All organic compounds tried, except carbon tetrachloride, yield hydrocyanic acid freely, but not cyanogen, as was proved by chemical tests. When chlorine is present, cyanogen chloride is formed. Benzene yields (almost certainly) cyanobenzene. (6) The intensity of the cyanogen spectrum with organic compounds is no index of the quantity of hydrocyanic acid being formed. Preponderance of the red cyanogen bands is associated with cyanogen chloride or bromide. On a general view of the evidence, there does not appear to be any definite connection between the development of spectra by active nitrogen and the chemical actions in progress.—Dr. J. A. Marker and Dr. G. W. C. Kaye: The electrical emissivity and disintegration of hot metals. Preliminary experiments have been carried out on the volatilisation and electrical emissivity of a number of metals, mostly in nitrogen at reduced pressures. The metals were heated by alternating current and no applied potential was employed, (1) The emission of positive electricity occurs at temperatures from about 1000° to 1400° C. For metals which melt within this range, a sudden and marked increase in the positive current often occurred at the liquefying point-due, probably, to the sudden release of occluded gas. (2). Oxygen appears to augment the positive current. (3) At higher temperatures, negative electricity predominates and increases rapidly with the temperature. The negative current attained with iridium at the melting point was 80 milliamperes, with tantalum at 1670° C. 220 microamperes, with iron at the melting point 90 microamperes. In the case of carbon in air at atmospheric pressure, an ionisation current of 3½ amperes was obtained. (4) The negative current at moderate pressures appears to be largely increased if the conditions are such that considerable sputtering of the metal occurs. (5) The negative currents are probably a consequence of chemical reaction between the metal and the surrounding gas. (6) Carbon becomes plastic in the neighbourhood of 2500° C. At such temperatures it. also readily sublimes.—Dr. A. O. Rankine: A method of measuring the viscosity of the vapours of volatile liquids, with an application to bromine. In this method of determining viscosities the rate of transpiration of the vapour through a capillary tube is controlled by the vapour pressures of the liquid itself, a difference of pressure being established in the process of virtually distilling the liquid through the capillary. The pressures can be estimated without the use of mercury gauges—a state of affairs especially desirable in the case of the halogens. The viscosities of unsaturated bromine vapour over the approximate range 10° C. to 250° C. have been measured, and, except at the lowest temperatures, are found to agree well with Sutherland's formula, not-withstanding the fact that all the temperatures are below the critical.—E. E. Fournier d'Albe: The efficiency of selenium as a detector of light. The efficiency of a selenium preparation used as a detector of light is defined as the amount of additional conductivity imparted to it by the unit of incident light. Since many factors affect the efficiency of a given selenium bridge, standard conditions are chosen, chief among them being an illumination of one lux. The law of light action is studied, and the total effect is shown to be proportional to the square root of the incident energy, while the instantaneous effect is proportional to the energy. This is verified down to an illumination of 0-00001 metre-candle. It is shown that selenium is the most efficient light detector known, that it is capabfe of discriminating minute differences of luminous intensity far beyond the capacity of the eye, and that, with suitable means of detecting minute currents, it should offer a means of testing the quanta theory of light by direct experiment.—A. E. Oxley: The Hall effect in liquid electrolytes. Experiments have been made on aqueous solutions of copper sulphate, silver nitrate, cadmium sulphate, and on copper sulphate gel. Each substance was placed in a small cell of glass or mica, and was subjected to a uniform magnetic field. A Paschen galvanometer was used to measure the transverse potential difference. In a uniform magnetic field this transverse potential difference is due partly to a true Hall effect (depending on the difference of the ionic mobilities), and partly to a concentration Hall effect (depending on the sum of the ionic mobilities). The latter effect is primarily the one which has been measured in this research, and the former, which is smaller, is included. Eight experiments have been made, and the transverse potential differences, which changed sign on reversal of the magnetic field, have been found to agree with the calculated values. The relation between the transverse potential difference and the intensity of the magnetic field, for an aqueous solution of copper sulphate, is linear.—Prof. W. B. Morton: The displacements of the particles and their paths in some cases of two-dimensional motion of a frictionless liquid.—S. Chapman: The diurnal variations of the earth's magnetism produced by the moon and sun.—Prof. H. A. Wilson and Marjorie Wilson: The electric effect of rotating a magnetic insulator in a magnetic field.—A. Hopwood: The magnetic materials in claywares. The author has rfound that white, cream, grey, yellow, buff, red, or brown claywares are feebly or moderately magnetic owing to the presence of unfused grains of unchanged ferruginous minerals and fused globules of complex ferruginous silicates; while flashed, brindled, or blue claywares are always strongly magnetic owing to the presence of complex ferruginous silicates and finely disseminated magnetic oxide of iron. The origin of the-complex ferruginous silicates in claywares is quite different from that of the magnetic oxide of iron. While the latter is produced either by the orientation of the magnetite, originally present in the clays, or by the reducing action of the kiln gases on the precipitated or colloid oxides, hydroxides, or carbonates of iron disseminated throughout the clays, the former are produced by the fusion of the granular or concretionary ferruginous minerals, i.e. iron pyrites, siderite, hasmatite, magnetite, biotite, &c., occurring in Sthe olays with the surrounding matrix.—A. Hopwood and C. Weizmann: Synthesis of the anhydrides of o-aminoacyl glucosamines.—>H. S. Jones: The flexure of telescope mirror-discs arising from their weight, and its influence upon resolving power.—Prof. W. H. Young: Fourier series and functi of bounded variation. In the present communication it is shown that in a number of fundamental theorems the derived series of the Fourier series of a function of bounded variation may take the place of the Fourier series of a summable function, and this even when the function of bounded variation is not continuous, or still less an integral. In particular, the coefficients of such a series may be used as convergence factors, with results which approximate to, or are even identical with, those obtained when the convergence factors are the coefficients of a Fourier series. The use of these convergence factors transforms, in fact, when the function of bounded variation is odd, a Fourier series into a Fourier series, and an allied series into a Fourier series when the function of bounded variation is even.—Prof. W. H. Young: A condition that a trigonometrical series should have a certain form. In the present communication a necessary and sufficient condition that a trigonometrical series should have a form in which its coefficients are expressible in terms of Stieltjes integrals with respect to a function of bounded variation is obtained.—Prof. W. H. Young: Trigonometrical series the Cesaro partial summations of which oscillate finitely.
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Societies and Academies . Nature 91, 470–472 (1913). https://doi.org/10.1038/091470a0
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DOI: https://doi.org/10.1038/091470a0